1. Field of the Invention
The present invention relates generally to a steam cooled gas turbine system and more particularly to a steam cooled gas turbine system in which temperature and flow rate of cooling steam are efficiently controlled and heating of fuel and cooling of gas turbine blade cooling air are carried out by steam generated at a waste heat recovery boiler.
2. Description of the Prior Art
FIG. 26 is a diagram of a steam cooled gas turbine system in the prior art. In FIG. 26, the prior art steam cooled gas turbine system is constructed of a gas turbine 8, a waste heat recovery boiler 9 and a steam turbine 29. In the gas turbine 8, suction air, is taken into a compressor 2 and compressed to a predetermined pressure. The compressed air is partially used for cooling a gas turbine blade, but most of the compressed air is led into a combustor 3 to be mixed with fuel 7 for generation of a high temperature gas. The high temperature gas enters a turbine 6 and expands to accomplish work, and a turbine output after deduction of a compressor output is converted into an electric power at a generator 1. On the other hand, outlet steam from a high pressure turbine 21 flowing through piping 101 is partially supplied into the turbine 6 for cooling the gas turbine blade via a cooling steam supply piping 101a. This steam is heated by cooling a steam cooled blade 51, and is recovered into an inlet of an intermediate pressure turbine 22 via cooling steam recovery piping 102. Thus, for cooling the gas turbine blade, the air bled from the compressor 2 and a portion of the outlet steam of the high pressure turbine 21 are used.
While outlet air of the compressor 2 is partially used for blade cooling in the turbine 6, this air, being of a high temperature, is cooled to a predetermined temperature at a blade cooling air cooler 4 using a cooling fan 5 and is then used for the turbine blade cooling. Thus, the air led from the compressor 2 is cooled once at the blade cooling air cooler 4 using the cooling fan 5, and then supplied into the turbine 6.
In the waste heat recovery boiler 9, outlet steam from a low pressure turbine 23 is converted into water from steam at a condenser 25. Then, the water is pressurized at a feed water pump 26 and heated at a feed water heater 10 to become saturated water. This saturated water is separated into three systems of water. The first system becomes saturated steam at a low pressure evaporator 11 and becomes superheated steam at a low pressure superheater 15 and is then supplied to an inlet of the low pressure turbine 23. The second system is pressurized to a predetermined pressure at an intermediate pressure pump 28, becomes saturated water at an intermediate pressure economizer 12, becomes saturated steam at an intermediate pressure evaporator 14, becomes superheated steam at an intermediate pressure superheater 16, and is then supplied to an inlet of a reheater 20. The third system is pressurized to a predetermined pressure at a high pressure pump 27, becomes saturated water at a first high pressure economizer 13 and a second high pressure economizer 17, becomes saturated steam at a high pressure evaporator 18, becomes superheated steam at a high pressure superheater 19, and is then led into the high pressure turbine 21. The mentioned superheated steam enters the high pressure turbine 21, the intermediate pressure turbine 22 and the low pressure turbine 23, respectively, to expand for generating an output, and this output is converted into electric power at a generator 24.
With respect to the above-mentioned cooling by steam, it is impossible to use the steam in a quantity in excess of that of the steam obtainable at the outlet of the high pressure turbine 21. Hence, in order to secure a spare quantity of the available steam, it is preferable to reduce the flow rate of the cooling steam to the extent possible. Also, if less cooling steam is made, it becomes possible to control the temperature of the steam, after the steam is used for cooling, with less variation in the quantity of the cooling steam. Especially, if the temperature of the cooling steam heated during the cooling is maintained at a predetermined level, it will not only enhance the reliability and life of the cooled blade, rotor, pipings, etc. of the gas turbine, but it will also ensure an operation without damaging the enhanced combined efficiency. In order to reduce the quantity of the cooling steam, it is necessary to reduce the temperature of the cooling steam.
Thus, while the temperature of the cooling steam is necessary to be maintained lower to enhance the reliability of the cooled blade or the like, in the system shown in FIG. 26, the cooling steam supply temperature is determined by the outlet condition of the high pressure turbine 21, and it is difficult to further reduce the cooling steam temperature in this system.
Also, the air bled from the compressor for cooling the gas turbine blade is once cooled at the blade cooling air cooler 4 using the cooling fan 5 to be supplied into the turbine 6, as mentioned above, and the heat obtained by such cooling is discharged outside in vain. This causes a reduction in the thermal efficiency (gas turbine efficiency and combined efficiency) of the gas turbine and of a combined cycle system using this gas turbine. Moreover, the fuel 7 is supplied into the combustor 3 without being heated (preheated).
In view of the problems in the prior art, therefore, it is an object of the present invention to provide a steam cooled gas turbine system in which the system is made such that cooling of a turbine blade is done by steam partially taken from an outlet of a high pressure turbine, and the temperature of this steam is adjusted by cooling water taken from a waste heat recovery boiler. A cooling steam supply system is made such that a moving blade, a stationary blade and a combustor transition piece are supplied with steam via their respective separate systems so that the steam supplied to the stationary blade and the combustor transition piece may be of a temperature higher than the steam supplied to the moving blade to thereby obtain a higher effect of the cooling by steam in the respective steam systems, and also so that preheating of fuel is done to thereby enhance the combined efficiency.
In order to achieve this object, the present invention provides the following,
(1) A steam cooled gas turbine system comprises a steam turbine having a high pressure turbine, an intermediate pressure turbine, and a low pressure turbine; a condenser for condensing exhaust steam of the low pressure turbine of the steam turbine; a gas turbine having a compressor for compressing air, a combustor for combusting fuel with the air coming from the, compressor, and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator; a cooling steam system for cooling a high temperature portion of the gas turbine including a high temperature portion of the combustor and a high temperature portion of a blade of the turbine; and a waste heat recovery boiler fed with exhaust gas from the gas turbine so as to heat and vaporize condensed water coming from the condenser for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively. In the cooling steam system, a heat exchanger effects a heat exchange so that outlet steam from the high pressure turbine flowing through the heat exchanger is cooled and supplied into at least one of the high temperature portions of the gas turbine so as to be cooled, and is then recovered into the waste heat recovery boiler. Cooling water coming from the waste heat recovery boiler and flowing through the heat exchanger is heated and is then recovered into the waste heat recovery boiler.
(2) A steam cooled gas turbine system comprises: a steam turbine having a high pressure turbine, an intermediate pressure turbine, and a low pressure turbine; a condenser for condensing exhaust steam of the low pressure turbine of the steam turbine; a gas turbine having a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor, and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator; a cooling steam system for cooling a high temperature portion of the gas turbine including a high temperature portion of the combustor and a high temperature portion of a blade of the turbine; and a waste heat recovery boiler fed with exhaust gas from the gas turbine so as to heat and vaporize condensed water coming from the condenser for supplying steam to the high pressure, intermediate pressure, and low pressure turbines, respectively. In the cooling steam system, a water sprayer supplies a high pressure water from the waste heat recovery boiler via a demineralizer into a passage for leading cooling steam from an outlet of the high pressure turbine into at least one of the high temperature portions of the gas turbine. A drain separator is interposed in a passage between the water sprayer and at least one of the high temperature portions. The cooling steam, from which drainage has been removed by the drain separator, is supplied into at least one of the high temperature portions for cooling thereof, and is then recovered into the waste heat recovery, boiler.
(3) In the steam cooled gas turbine system mentioned in section (1) or (2), the high temperature portion of the gas turbine may be a moving blade.
(4) In the steam cooled gas turbine system mentioned in section (1) or (2), the high temperature portion of the gas turbine may be a stationary blade, and the steam heated by cooling the stationary blade can be recovered into the waste heat recovery boiler.
(5) In the steam cooled gas turbine system mentioned in section (1) or (2), the high temperature portion of the gas turbine may be a combustor transition piece, and the steam heated by cooling the combustor transition piece can be recovered into the waste heat recovery boiler.
(6) In the steam cooled gas turbine system mentioned in section (1) or (2), the high temperature portion of the gas turbine may be a moving blade and a stationary blade, and the steam heated by cooling the stationary blade can be recovered into the waste heat recovery boiler.
(7) In the steam cooled gas turbine system mentioned in section (1) or (2), the high temperature portion of the gas turbine may be a moving blade, a stationary blade, and a combustor transition piece, and the steam heated by cooling the stationary blade and the combustor transition piece can be recovered into the waste heat recovery boiler.
(8) In the steam cooled gas turbine system mentioned in section (1) or (2), the high temperature portion of the gas turbine may be a stationary blade and a combustor transition piece, and the steam heated by cooling the stationary blade and the combustor transition piece can be recovered into the waste heat recovery boiler.
(9) In the steam cooled gas turbine system mentioned in any one of sections (1) to (8), the cooling steam system may have a flow regulating valve for regulating a flow rate of the steam so as to correspond to a cooling ability of the high temperature portion of the gas turbine.
(10) In the steam cooled gas turbine system mentioned in section (9), a fuel inflow passage of the combustor of the gas turbine has a fuel heater for heating fuel using steam coming from the waste heat recovery boiler, and the steam cooled by heating the fuel can be recovered into a feed water heater. A portion of the outlet water from the feed water heater flows through a blade cooling air cooler for cooling blade cooling air of the turbine, and the water heated by cooling the blade cooling air can be recovered into the waste heat recovery boiler.
(11) A steam cooled gas turbine system comprises: a steam turbine having a high pressure turbine, an intermediate pressure turbine, and a low pressure turbine; a condenser for condensing exhaust steam of the low pressure turbine of the steam turbine; a gas turbine having a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor, and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator; a cooling steam system for cooling the combustor and a blade of the turbine; and a waste heat recovery boiler having components of a feed water heater, an intermediate pressure economizer, a first high pressure economizer, a second high pressure economizer, a low pressure superheater, an intermediate pressure superheater, a high pressure superheater, a high pressure evaporator, and a reheater, and being fed with exhaust gas from the gas turbine so that condensed water coming from the condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively. The cooling steam system has a heat exchanger for effecting a heat exchange so that outlet steam from the high pressure turbine flowing through the heat exchanger is cooled and supplied into a moving blade of the gas turbine for cooling thereof. The steam is then recovered into the reheater, and cooling water coming from the first high pressure economizer and flowing through the heat exchanger is heated and is then recovered into the high pressure evaporator.
(12) A steam cooled gas turbine system comprises: a steam turbine having a high pressure turbine, an intermediate pressure turbine, and a low pressure turbine; a condenser for condensing exhaust steam from the low pressure turbine of the steam turbine; a gas turbine having a compressor for compressing air, a combustor for combusting fuel with the air coming from the, compressor, and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator; a cooling steam system for cooling the combustor and a blade of the turbine; and a waste heat recovery boiler having components of a feed water heater, an intermediate pressure economizer, a first high pressure economizer, a second high pressure economizer, a low pressure superheater, an intermediate pressure superheater, a high pressure superheater, a high pressure evaporator, and a reheater. The waste heat recovery boiler is fed with exhaust gas from the gas turbine so that condensed water coming from the condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively. The cooling steam system has a water spray rate control valve for leading high pressure water from the feed water heater. A demineralizer is connected to the water spray rate control valve, a water sprayer is connected to the demineralizer for spraying the high pressure water into a passage for leading cooling steam from an outlet of the high pressure turbine to be supplied into a moving blade of the gas turbine, and a drain separator is interposed in a passage between the water sprayer and the moving blade. The cooling steam, from which drainage has been removed by the drain separator, is supplied into the moving blade for cooling thereof and is then recovered into the reheater.
(13) A steam cooled gas turbine system comprises: a steam turbine having a high pressure turbine, an intermediate pressure turbine, and a low pressure turbine; a condenser for condensing exhaust steam from the low pressure turbine of the steam turbine; a gas turbine having a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor, and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator; a cooling steam system for cooling the combustor and a blade of the turbine; and a waste heat recovery boiler having components of a feed water heater, an intermediate pressure economizer, a first high pressure economizer, a second high pressure economizer, a low pressure superheater, an intermediate pressure superheater, a high pressure superheater, a high pressure evaporator, and a reheater. The waste heat recovery boiler is fed with exhaust gas from the gas turbine so that condensed water coming from the condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure, and low pressure turbines, respectively. The cooling steam system has a water spray rate control valve for leading a high pressure water from the feed water heater. A demineralizer is connected to the water spray rate control valve, a water sprayer is connected to the demineralizer for spraying the high pressure water into a passage for leading cooling steam from an outlet of the high pressure turbine to be supplied into a moving blade of the gas turbine. A drain separator is interposed in a passage between the water sprayer and the moving blade, and the cooling steam, from which drainage has been removed by the drain separator, is supplied into the moving blade for cooling thereof and is then recovered into the reheater. A heat exchanger side flow regulating valve is provided near a steam inlet of the reheater in the outlet steam piping of the high pressure turbine connected to the steam inlet of the reheater and an outflow side flow regulating valve in a cooling steam outlet passage of each moving blade, a stationary blade, and a combustor transition piece. A fuel inflow passage of the combustor has a fuel heater for heating fuel by outlet steam of the intermediate pressure economizer, and the steam cooled by heating the fuel is recovered into the feed water heater. A portion of the outlet water from the feed water heater flows through a blade cooling air cooler for cooling blade cooling air of the turbine, and the water heated by cooling the blade cooling air is recovered into the high pressure evaporator.
In section (1), a portion of the high pressure turbine outlet steam is extracted to be used as cooling steam. This steam is cooled at the heat exchanger to then be supplied into the high temperature portion of the gas turbine. The steam heated by so cooling the high temperature portion of the gas turbine is recovered into the waste heat recovery boiler. On the other hand, for cooling the steam at the heat exchanger, a portion of the water from the waste heat recovery boiler is removed as cooling water to be supplied into the heat exchanger. This water heated by cooling the steam is recovered into an inlet side, or a high temperature side, of the waste heat recovery boiler. In a system in which the heat given to the cooling water at the heat exchanger is discharged outside, the combined efficiency is reduced. However, in section (1), this heat given to the cooling water is recovered into the high temperature side of the waste heat recovery boiler. Thus, without the combined efficiency being hurt, reduction of the temperature of the cooling steam for cooling the high temperature portion of the gas turbine can be obtained. Thus, according to the system of the present invention, while the combined efficiency is in no case reduced, the reduction in the supply temperature and supply quantity of the cooling steam becomes possible. Moreover, the temperature of the steam, after being used for the cooling, can be controlled with less variation in the quantity of the cooling steam. Hence, a spare quantity of the available steam is ensured, and the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured.
In section (2), the system is constructed such that the heat exchanger used in section (1) is eliminated, and instead a water spraying device, including the water spray rate control valve, the demineralizer, the water sprayer and the drain separator, for spraying water taken from the waste heat recovery boiler, is employed. By such construction, the water spray rate is controlled by the water spray rate control valve, and control of the supply temperature of the cooling steam for cooling the high temperature portion of the gas turbine can be done more quickly than in section (1). The demineralizer is a type that is usually used for removing dissolved minerals in the condenser of a supercritical pressure plant or a nuclear plant, and impurities in the water are removed by the demineralizer. Also, the drain separator is used for separating drainage that is generated in a small quantity after the water is sprayed into the steam by the water sprayer so that the cooling steam, from which drainage has been removed, is supplied for the cooling. Thus, a quicker reduction in the supply temperature and supply quantity of the cooling steam of the gas turbine high temperature portion becomes possible. Also, the temperature of the steam, after being used for cooling, can be controlled with less variation in the quantity of the cooling steam. Hence, a spare quantity of the available steam is ensured, and the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured.
In sections (3) to (8), the respective high temperature portions of the gas turbine to be cooled in sections (1) or (2) are selected as follows: the moving blade only in section (3), the stationary blade only in section (4), the combustor transition piece only in section (5), the moving blade and stationary blade in section (6), the moving blade, stationary blade and combustor transition piece in section (7), and the stationary blade and combustor transition piece in section (8). Thus, the respective portions of the gas turbine are cooled and, like in section (1) or (2), reduction in the respective supply temperature and supply quantity of the cooling steam becomes possible. Also, the temperature of the steam, after being used for the cooling, can be controlled with less variation in the quantity of the cooling steam. Hence, a spare quantity of the available steam is ensured, and the reliability and life elongation of the cooled blade, rotor and pipings can be ensured.
In section (9), a flow regulating valve is provided at each appropriate position in the cooling steam system and, by opening and closing the valves, the supply temperature of the cooling steam for cooling the gas turbine high temperature portion becomes controllable at any load state from the rated load to the partial load. Thus, the supply temperature of the cooling steam becomes controllable without changing the supply quantity of the cooling steam, and the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured. Also, control of the respective recovery steam temperature becomes possible, so that the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured. In each of the flow regulating valves, if the valve is opened, the supply quantity of the cooling steam is increased and the recovery temperature of the cooling steam is reduced. If the valve is closed, the supply quantity of the cooling steam is reduced and the recovery temperature of the cooling steam is elevated. In the construction using the water spray rate control valve, demineralizer, water sprayer and drain separator, the water spray rate is controlled by the water spray rate control valve and, by adding the flow regulating valves to this construction, a quick control of the supply temperature of the cooling steam to be supplied into the gas turbine high temperature portion becomes possible. Also, as described with respect to section (2), a quick reduction in the supply temperature and supply quantity of the cooling steam becomes possible, and the temperature of the steam, after it is used for cooling, can be controlled with less variation in the quantity of the cooling steam. Hence, a spare quantity of the available steam is ensured and the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured.
In section (10), the fuel is heated at the fuel heater. Also, a portion of the water on an outlet side, or a low temperature side, of the waste heat recovery boiler is supplied into the blade cooling air cooler for effecting a heat exchange. At the blade cooling air cooler, the water cools the blade cooling air to be supplied into the gas turbine high temperature portion, and the water heated by cooling the air is then recovered into the waste heat recovery boiler. Thus, the heat that has been so far discharged outside by the cooling fan is recovered into the waste heat recovery boiler, and the combined efficiency is enhanced.
In section (11), in order to cool the steam cooled moving blade, a portion of the high pressure turbine outlet steam is extracted to be used as cooling steam for the steam cooled moving blade. This steam is cooled at the heat exchanger and then supplied into the steam cooled moving blade of the gas turbine. The steam heated by so cooling the moving blade is recovered into the middle portion of the reheater. On the other hand, for cooling the steam at the heat exchanger, a portion of the outlet water from the first high pressure economizer is taken as cooling water to be supplied into the heat exchanger. This water heated by so cooling the steam is recovered into an inlet of the high pressure evaporator. In a system in which the heat given to the cooling water at the heat exchanger is discharged outside, the combined efficiency is reduced. However, in section (11), this heat given to the cooling water is recovered into the inlet side, or the high temperature side, of the waste heat recovery boiler. Thus, without the combined efficiency being hurt, the temperature of the cooling steam for cooling the high temperature portion of the gas turbine can be reduced. Thus, according to the system of the present invention, while the combined efficiency is in no case reduced, the reduction in the supply temperature and supply quantity of the cooling steam becomes possible. Moreover, the temperature of the steam, after being used for the cooling, can be controlled with less variation in the quantity of the cooling steam. Hence, a spare quantity of the available steam is ensured, and the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured.
In section (12), the system is constructed such that the heat exchanger as used in section (11) is eliminated, and instead a water spraying device, including the water spray rate control valve, the demineralizer, the water sprayer and the drain separator, for spraying water taken from the outlet water of the high pressure pump is employed. By such construction, the water spray rate is controlled by the water spray rate control valve, and control of the supply temperature of the cooling steam for cooling the moving blade of the gas turbine can be done more quickly than in section (11). The demineralizer is one that is typically used for removing dissolved minerals from the condenser of a supercritical pressure plant or a nuclear plant, and impurities in the water are removed by the demineralizer. Also, the drain separator is used for separating drainage that is generated in a small quantity after the water is sprayed into the steam by the water sprayer so that the cooling steam from which drainage has been removed is supplied for the cooling. Thus, as the feature of the present invention, a quicker reduction in the supply temperature and supply quantity of the cooling steam for cooling the moving blade becomes possible. Also, the temperature of the steam, after being used for cooling, can be controlled with less variation in the quantity of the cooling steam. Hence, a spare quantity of the available steam is ensured and the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured.
In section (13), the heat exchanger is eliminated and instead, like in section (12), the water spray rate control valve, demineralizer, water sprayer and drain separator are employed. By such construction, the water spray rate is controlled by the water spray rate control valve, and a quicker control of the supply temperature of the moving blade cooling steam becomes possible. Also, by cooling the blade cooling air at the blade cooling air cooler, the moving blade is cooled efficiently and, as described with respect to section (12), the quicker reduction in the supply temperature and supply quantity of the moving blade cooling steam becomes possible. Further, by controlling the flow regulating valves, the flow rate of the steam can be controlled appropriately. Thus, the temperature of the steam, after being used for the cooling, can be controlled with less variation in the quantity of the cooling steam. Hence, a spare quantity of the available steam is ensured, and the reliability and life elongation of the cooled blade, rotor, and pipings can be ensured.